1. Field of the Invention:
The present invention relates generally to serial radiographic systems and more particularly to a system for obtaining a visible radiation image by use of a stimulable phosphor sheet.
2. Discussion of Background:
When certain kinds of phosphors are exposed to radiation such as X-rays, .alpha.-rays, .beta.-rays, .gamma.-rays or ultraviolet rays, they store a part of the energy of the radiation. Then, when the phosphor which has been exposed to the radiation is exposed to a stimulating ray such as visible ray, light is emitted from the phosphor in the pattern of the stored energy of the radiation. A phosphor exhibiting such properties is referred to as a stimulable phosphor.
A serial radiographic system adapted especially for using the stimulable phosphor is described in U.S. Pat. No. 4,236,078, entitled, METHOD AND APPARATUS FOR RECORDING AND REPRODUCING A RADIATION IMAGE, issued to Kotera et al. This patent discloses a method and apparatus of radiation image recording and reproducing which employs a radiation image storage panel including a stimulable phosphor for medical diagnosis. The stimulable phosphor is first exposed to radiation to have a radiation image stored therein and is then scanned with a stimulating ray which causes it to emit light in the pattern of the stored image. The light emitted from the stimulable phosphor upon stimulation thereof is photoelectrically detected and converted to an electric signal which is processed as desired to reproduce a visible image of a quality suitable for viewing and diagnostic purposes.
In the radiation image recording and reproducing method described above, the final visible image may be reproduced in the form of a hard copy or may be displayed on a cathode ray tube. The stimulable phosphor sheet used in this method may take various forms such as panel, drum or the like, which are herein generally referred to as an image plate (IP). For reasons of economy, it is desirable that the IP be used repeatedly in many separate radiographic operations, such as 1,000 operations.
In serial radiography, a series of radiographs are produced by sequentially feeding a series of IPs, one at a time, to an exposure station. The exposure station is aligned with a source of X-rays which directs a beam of X-rays through the exposure station to expose the IPs.
A stack of IPs is stored in a supply magazine. A transport and drive system sequentially transports the IP from the supply magazine to the exposure station at high speed. After exposure the IPs are transported to, and deposited in, a receiving magazine. The transport and drive system concurrently delivers an unexposed IP to the exposure station and an exposed IP to the receiving magazine.
Such a system is required to be compact, to expose IPs at high rates, and to avoid any possibility of an IP being scratched or otherwise damaged during transport or exposure to assure that a timely exposure will accurately record an event of short duration.
An especially severe problem for the radiographic system above discribed is damage on the phosphor layer of the stimulable phosphor sheet (IP), and results in data loss of the image, which is highly undesirable in radiographic system.